This application is a national stage entry under 35 U.S.C. xc2xa7 371 of PCT/JR00/01901 filed Mar. 28, 2000.
The present invention relates to a process for the preparation of (E)-3-(1-propenyl)-2-isoxazoline useful as an intermediate for producing agricultural chemicals, drugs and others.
Only one known process for the preparation of (E)-3-(1-propenyl)-2-isoxazoline is that described by P. A. Wade, et al in J. Org. Chem., 62, 3671-3677(1997): The E isomer is obtained by reduction of 3-(1-propenyl)-2-isoxazoline (A), followed by isomerization of the produced mixture of Z and E isomers. The compound (A) is produced from nitroisoxazoline and propyne lithium with many steps, being very expensive.
It is an object of the present invention to provide an industrially advantageous process for the preparation of (E)-3-(1-propenyl)-2-isoxazoline.
The present invention relates to a process for the preparation of (E)-3-(1-propenyl)-2-isoxazoline, characterized by a reaction of crotonaldehyde with hydroxylamine, followed by a reaction of the produced oxime, while changing to nitrile oxide, with ethylene.
A process of the present invention is described below: 
The present invention relates to a method of obtaining (E)-3-(1-propenyl)-2-isoxazoline in a way that crotonaldehyde is treated with hydroxylamine in a solvent and then ethylene is blown into the produced oxime while changing to nitrile oxide. It is possible to isolate the oxime. It is however preferable to use the solution itself in the next reaction without isolating it.
An aqueous solution of hydroxylamine or its hydrochloride can be used.
Any solvent can be used for the reaction if it does not react with nitrile oxide. Examples of solvents used include chlorine compounds such as chloroform, aliphatic hydrocarbons such as hexane, and aromatic hydrocarbons such as benzene and toluene.
An oximation reaction can be carried out at a temperature of 40xc2x0 C. or below. However, it is generally preferable to do at 10xc2x0 C. or below.
Examples of agents used to generate nitrile oxide include oxidizing agents such as sodium hypochlorite, and halogenating agents such as N-chlorosuccinimide (NCS). When the latter is used, a weak base, such as potassium hydrogen carbonate, is required.
A reaction of nitrile oxide with ethylene is usually carried out in a way that ethylene is blown into a solution containing nitrile oxide at the atmospheric pressure.
In the present invention, ordinary work-up are applied after the completion of the reactions. It is possible to separate and purify the product by distillation or column chromatography (with a mixed solvent of ethyl acetate and n-hexane).
IR, NMR, MS and other means were used to identify the products.